Construction Scheme of PE Power Pipe Buried Outdoor: Anti-corrosion and Mechanical Damage Protection

PE power pipes are widely used in outdoor power pipeline direct-buried projects due to their advantages such as corrosion resistance, light weight and convenient construction. However, soil corrosion and external load impact in direct-buried environments can easily lead to pipeline damage, and long-term protection needs to be achieved through scientific construction schemes. The following describes the key technical points from four aspects: construction preparation, anti-corrosion design, mechanical protection and quality control.

First, pre-construction environmental assessment and material preparation

Corrosive testing of soil is required before construction, and the corrosion grade is determined through pH determination, resistivity test and soil composition analysis. For strongly corrosive soil (pH 9.0), reinforced anti-corrosion measures are required. At the same time, check the quality of PE pipe to ensure that it meets the GB/T 13663.2 standard, focusing on checking the deviation of pipe wall thickness, tensile strength and weather resistance indicators. Unqualified pipes are strictly prohibited from entering the site.

Second, multi-layer anti-corrosion system construction technology

1. Pipe body protection

selects PE100 grade pipes that meet the engineering pressure grade to ensure the purity of raw materials (carbon black content 2.5% -3.0%) to improve the anti-ultraviolet aging ability. For the interface part, the electric fusion connection process is adopted, and the cleanliness of the welding surface needs to be guaranteed during construction. The welding parameters are strictly carried out according to the process curve provided by the pipe manufacturer. After welding, 100% air pressure testing is carried out (test pressure 0.15MPa, no pressure drop for 30 minutes).

2. Composite protective layer design

In moderately corrosive soil environments, double-layer protection of "PE pipe + heat shrinkable sleeve" can be used; in strong corrosive environments, epoxy coal pitch anti-corrosion coating (dry film thickness 0.4mm) needs to be added. During construction, the surface of the pipe is sandblasted for rust removal (up to Sa2.5 grade), and then the primer is coated by airless spraying process. After wrapping the glass fiber cloth, the topcoat is applied to form a complete anti-corrosion system.

Third, comprehensive protection measures for mechanical damage

1. Buried depth and cushion design

The buried depth under the roadway is not less than 0.7m, the sidewalk is not less than 0.5m, and it needs to be deepened to 1.0m when crossing the motorway. The bottom of the trench is laid with a 200mm thick graded sand and gravel cushion (particle size 5-31.5 mm), which is tamped with a flat vibrator (compaction degree 90%) to avoid direct contact with sharp objects in the pipeline.

2. Backfill material and process control

Adopt layered backfill method: The first layer (300mm below the top of the pipe) is made of fine sand with a particle size of 5mm, which is manually tamped; the second layer (300-500mm) is backfilled with plain soil and compacted by a small road roller (compaction degree 93%); the upper layer is backfilled according to the requirements of the roadbed. It is strictly forbidden to use construction waste or frozen soil blocks during the backfill process, and mechanical rolling shall not be used within the 500mm range of the top of the pipe.

3. Warning and isolation measures

Continuously lay a warning tape (width 200mm, printed with the words "power cable, no excavation") at 300mm above the top of the pipe, and the lap length of the warning tape is 100mm. When crossing the road or the area vulnerable to construction disturbance, MPP protection pipes (pipe diameter is larger than the two levels of the working pipe) need to be set up, and the two ends of the protection pipe extend to 2m outside the roadbed.

Fourth, construction quality control points

1. Interface quality control

Before electric fusion welding, the pipe should be straightened, and the staggered amount is 10% of the wall thickness. After welding is completed, it will naturally cool down for not less than 30 minutes, and it is strictly forbidden to move the pipe during the cooling process. Each welding port needs to be inspected for appearance (no bubbles, even flanging), and destructive tests are carried out according to the proportion of 5%.

2. Protective layer integrity test

Use an electric spark leak detector (voltage 30kV) to test the anti-corrosion coating, and no breakdown is qualified. For the heat shrinkable sleeve interface, the circumferential tensile strength is 15MPa and the peel strength is 70N/cm.

3. Completion acceptance standard

After the pipeline laying is completed, the elevation re-test (allowable deviation 50mm), coordinate re-test (allowable deviation 100mm) and airtightness test (test pressure 0.2MPa, pressure drop 0.02MPa for 1 hour of holding pressure) are required. The acceptance data should include complete documents such as soil test report, weld joint test record, and protective layer test data.

Through the above systematic protection measures, the direct buried service life of PE power pipes can be effectively extended to more than 50 years. In engineering practice, it is necessary to dynamically adjust the protection plan according to the on-site geological conditions, focusing on the interface treatment, backfill quality and the durability of warning signs to ensure the long-term safe and stable operation of power pipelines.